text:
Why do flying wires hum louder in a sideslip?
Page 50 of the Feb. 2021 issue of the EAA's magazine Sport Aviation reports that

Like any good vintage airplane, the Sea Bird likes to fly coordinated,
and the flying wires will sing out loud if the
ball
gets off-center.

Why would the wires hum or sing more when the airstream impinges from one side?
All else being equal, a sideslip converts some of the flow's transverse component to an axial component, from the wire's point of view.  (Like many airplanes, the Sea Bird's rigging is mostly parallel to the wing.)  That should reduce vibration, because axial motion in a wire under tension is hard to provoke: try bowing a violin with the bow nearly parallel to the string.

Is there really no tag for such wires, by one of their many names (bracing, flying, landing, incidence)?

The lines are on the top surface of the wing and may not be under tension on normal flight, so they would only be tight enough to resonate under certain conditions (low/negative lift, sideslip).

The photos in the print magazine show "landing wires" above the wing, "flying wires" below, and bracing wires at the wingtip pontoons and tail.  (But even the detail photos don't reveal any wires' cross section.)

Here is one reason.
It once was common for suspension wires to be flattened rather than circular in cross-section, to reduce drag. those wires were then aligned with the airflow past the wing and fuselage in cruise. However, any time that airflow was not aligned with the wires, they would present an angle of attack to the slipstream and generate lift, which would pull them out of position, stretch the wires, and twist them to increase the local AoA. Then the wires would shed a vortex, stall (killing the lift), untwist, snap back, and then get pulled out of position again, etc., etc. and the result was the wires would "sing".
You can think of this as a special case of aerodynamic flutter.

So the vibration is neither transverse nor axial, but torsional?  Neat!

The Sea Bird was 1935.  Is there a reference for which years noncircular wires were common?

they were used in the Ryan ST "Sport Trainer" which first flew in 1934. the flat wires are mentioned by James Gilbert in his book The Great Planes.

@CamilleGoudeseune The wires would always be non-circular as soon as the first engineer thought of the possibility which was probably right at the beginning.

@Nobody - I doubt there were any non-circular flying wires in the ww1 era

Invented in 1909.  First produced in 1917, by the RAF!  http://airbum.com/articles/Flyingwires.html


text:
How much do propellers stutter?
A photo in EAA's monthly magazine shows one propeller blade as a dozen distinct images rather than the usual smooth motion blur.  One explanation (this answer appears to have been deleted) for this is that a propeller at nominally 2300 rpm actually varies +-200 rpm as each cylinder fires, so when it's slower, it captures more sunlight glint.
Edit: this question is about propellers, not about a photo.  The photo is only a motivation, perhaps an incorrect one, for the question.
Is this plausible?

Piston engines have flywheels.
A 400 rpm change happening 2300 times per minute is a 17% change happening 38 times per second.  Jerry Lee Lewis would say that's a whole lotta shakin' goin' on.
Onboard GoPro videos with rolling shutter artifacts show the blades "bending" from root to tip smoothly, not jaggedly.

Comments are not for extended discussion; this conversation has been moved to chat.

The stutter would be at 2300/min for a two-cylinder engine (or 2-stroke single).  For an 8cylinder engine it would be four times that, or 150Hz or so.  For a 1000HP engine the output is about 450J per ignition cycle.  Estimating a flywheel effective radius of 200mm and mass 30kg the kinetic energy is around 350kJ and so the stutter would be less than 1%.  I’ve skipped most of the calculations there :-)

I would guess the "multiple images" are just light reflections from the water waves onto the propeller.

@alephzero Intriguing. Feel free to answer the linked question on photo.SE.

Mind showing us the math? Something doesn't add up here (pun intended). Putting out 1000hp at 150 powerstrokes/second would require about 4970 Joules/powerstroke. A typo perhaps?

@MikeSowsun this answer does not address why the photo appears as it does, because it answers the question asked: does a propeller stutter enough to explain the effect seen in the picture. There is question on photography.se that deals with the rest.

The question asks if this is plausible. It is not, the thing would make a horrendous noise and break up.

We can count more than 15 blade-images in that short arc of revolution of the propeller, so there's no way that each one corresponds to an individual firing of a cylinder.  Perhaps there is a resonant vibration involving a slight twisting of the blade, and the sun angle is such that this produces a strobing effect.
The suggestion of a 300 rpm variation between each individual firing of a piston is completely implausible.
Some sort of camera artifact seems a possibility.

Further, if the idea is [A] the prop is "slowing down and speeding up", it would have to be slowing down to something like 1/10th (!!!!!) or perhaps much less than that, to achieve such clear "lines" which are about 1/0th as thick as the "gaps".  Does there even exist a material which would make this much deccelleration / acceleration possible??  I imagine if you , say, put a large concrete block in front of a propellor (which is the sort of decceleration we're talking about, everything would explode in shards?

If [B] the idea is that the propellor is twisting in some way that it reflects (again, only for roughly 1/10th of each cycle) and then becomes unbent again (for the other roughly 9/10ths of each putative "reflection cycle") ... again it seems hard to believe any mechanical device could sustain such a regular twisting motion (indeed, apparently pretty smoothly along it's whole length, it seems)

As pointed out before, the variation is unlikely to be the first engine order of individual firing cylinders.
Over on the photography site they provided EXIF data, showing an exposure time 1/200s, which would lead to only 1500rpm (assuming the motion blur in the picture is 45deg), not the 2300rpm nominal.
The frequency in the picture is in the range of approx 3000Hz (1 event every 3 deg at 1500 rpm), which might be some eigenfrequency of the crankshaft-propeller arrangement. My estimation is though that the low order eigenfrequencies are lower, and the higher order eigenmodes would show nodes of zero displacement. The superposition might lead to something like in the image.
There's some (older) doc on propeller vibrations here:
https://nvlpubs.nist.gov/nistpubs/jres/21/jresv21n5p639_A1b.pdf
Personally, I find some digital photography artefact the more likely explanation (some sensor-readout .. effects)

This picture was taken using the type of LCD shutter that is essentially one large monochrome pixel. It becomes transparent when a voltage is applied.
The camera manufacturer probably used a square-wave (2 kHz is often recommended) to avoid damaging the shutter with a persistent DC bias. The inescapable deviations from the ideal waveform would be enough to cause the shutter to vary in transparency, probably between fully transparent and slightly dimmed.
Another possibility is that the clearing voltage contained a ringing artifact, a common result of attempting to apply a square wave to an electronic control.
The registering retina might have been either photosensitive film or a photocell array. The stuttering-image illusion is due to the nature of the shutter and independent of the recording tech.
I assume that the stuttering-image illusion will appear only when using this camera to photograph a fast moving brightly lit object, in this case a specular reflection of the sun on the polished blade. Note how the other propeller blade, which is not reflecting the sun, does not seem to stutter.
EDIT:
The numbers match.
Suppose the shutter is driven by a square wave oscillator (a DC bias might damage it). Each oscillator cycle produces two square waves, one in each direction, with a slight gap between due to the inevitable deviations from the ideal waveform. This would produce two propeller images per cycle.
At least one LCD shutter vendor recommends a 2KHz AC square wave. This would produce 2000 * 2 = 4000 images per second, or 240000 images per minute.
I count 12 separate propeller images in the photo, in an arc that appears to be about one-tenth of the complete circle. One engine rotation therefore would produce 120 images.
Suppose the aircraft engine is running at 2000 RPM. This would produce 120 * 2000 = 240000 images per minute, as expected.
These numbers are all ballpark guesses. 2000 RPM is a low power setting for most GA planes, but if the engine was running faster and the square wave oscillator was set to 3KHz instead of 2KHz, the numbers would still match.
This does not prove my theory but it does invite further investigation. Maybe I could get a grant.
EDIT:
The photographer, Jim Busha, reports that he used an unmodified Nikon D850, which definitely does not have an LCD electronic shutter. The D850 is perfectly capable of achieving all the electronic shutter functionality it needs simply by turning the image sensor on at the appropriate time.
My theory is disproved.

Interesting theory but wouldn't that be one super flawed camera? Professional photographers use slow shutters for aesthetic effect all the time and this kind of artifact is not acceptable.

@Roman: If the camera shutter is made slow on purpose the ringing will be on such a short timescale it won't matter.

@A.I.Breveleri , just to clarify, you state that you  know it was taken with a camera using that type of shutter.  Do you mean (A) somewhere it states which camera was used for the photo, and you know about that camera model, or do you mean (B) you have no idea which camera was used; but from looking at the photo you know that type of shutter must have been used. Can you please clarify  or B?

interesting idea but such cameras don't exist...

@Fattie: B. I know that such LCDs are manufactured (by e.g. Pimoroni Ltd, Meadowlark Optics, Inc., LC-Tec Displays AB) and sold to camera makers. I don't know what makes and models of cameras use them.

This is the correct answer I think. On modern long-exposure shots of motorways in the darkness you can sometimes see how head and tail lights don't produce a smooth streak but instead multiple fairly clear spots. I guess this is the same effect.

I'm afraid this answer is a completely wrong guess - because, quite simply, almost no cameras use the type of shutter mentioned here.

"almost no cameras"... My theory only requires one.

I am sorry, I was just being polite.  A few technical "cameras" used on production lines and the like use this technology.  As @szulat mentions, there are no such "cameras" in the sense of commercial or consumer cameras for photography.  Also, just to go down the rabbit hole, how would you explain the "bending" of both props (ie: as seen on every single digital photo ever taken of any spinning propellor, and as explained in vast detail in 100s of articles).

The linked question on Photo SE now includes the EXIF data.  Nikon D850.  Mainstream.  (This answer still belongs on Photo SE, not Aviation SE.)

Purely regarding the fact that the color is different on each side of the prop...
(Remarkably, even a couple of the current answers on the photography site are "puzzled" by this.)
Every photo, ever taken, of a propellor has a different reflection on one side than the other .... since .... props bend one way on one side, and the other way on the other side.

(I simply googled "photo of propellor" and (obviously) literally every single photo looks like this. These are the first four.)  (I guess this confirms there are no "flat" propellors, heh!)
I appreciate the question here is about engine stutter, but, a number of people have been puzzled by the different color on each side.

This addresses the question on the photography stack exchange, and commendably so, but, as it states, it doesn't address this question on the aviation stack exchange.  (Are the two sites' cultures more different than I'd guessed?  Is the overlap, ahem, blurrier?)

@CamilleGoudeseune , you're right, but the whole question (on both sites) is confusing beyond belief!  Notice for example the other answer on this site which is (frankly nonsensical) which deals only with the photography aspect, has numerous upvotes and comments that it "finally explains!" the effect.  My own answer which trivially explains the whole thing (every photo ever taken digitally of a prop has the two effects, repeats and bending), has downvotes!  On the photo site there's now a wholly astonishing discussion of how it's, no really, reflections of waves,....

(which magically change, or something unexplainable, at 10kHz), and then there's folks stunned at how the prop can be different colors on each side, and there's the original "pistons firing" thing which would be like confusing the heat of the sun with an icecube  :)   So .. I just thought this answer might clear up one aspect anyways  :O

I have never heard of a propellor stuttering in this way, at least not in normal flight. The calculations in the various answers to date put the vibration in the audio mid-range, to which our ears are most sensitive. The magnitude shown in the photo would be clearly audible if it were real, and the pilot would be throttling back and looking for an emergency landing place, not lazing around posing for a photo-shoot!
Now, I know this question is not about digital cameras, but the evidence supporting the question certainly is; the things are a menace when it comes to this kind of shot.
So it's pretty much a slam-dunk: the prop is not stuttering, the camera is.

Torsional vibration of the blades is also a possibility.

@Mark The argument applies to all vibration modes, torsional included.

It's nothing more than the usual "time aliasing" of any (digital) photo ever taken of any propellor.
There are 1,000 detailed explanations of this online ...
http://resourcemagonline.com/2015/11/why-your-camera-makes-airplane-propellers-look-so-weird/60421/
(Note that if you look carefully at the photo of the blue plane, you can see the typical "bending" as well - as with every single digital photo, ever taken, of a propellor you get two effects (a) bending and (b) repeats. Exactly as in the photo here. Like every single digital photo, ever taken, of a propellor.)
Please note that the answer over here:  https://photo.stackexchange.com/a/121533 (which the writer states is a "theory") is "unbelievably incorrect".

Here's a photo that perfectly shows the "bending effect" will be either more or less depending on the geometry domain.
https://www.dpreview.com/forums/thread/3692327?page=2

This perfectly shows that the "bending effect" can be either extreme or gentle - gentle seen on the blue plane image.
You can see in a zillion photos that you get repeats of the blade (more than the actual number of blades!)  This is completely commonplace and applies to literally every photo, ever, taken digitally of a prop.
http://sbiii.com/aviatn-7.html

The image just above is literally identical to the blue plane image, except the time domain is a bit different.
(For the record, the idea that the propellor could be revolving in a step-wise fashion is bonkers.)
Every single digital photo even taken of a prop shows
A - multiples
B - the bending effect
the blue plane photo is wholly unremarkable (indeed I instantly googled dozens of images where the "multiples are close together" as in the blue plane image).
BTW I realize the headline question here is "how much does a propellor stutter" but the idea is so silly, and the facts on that have already been noted in the other answers.

The effect pictured is very different from the rolling shutter effect described in the linked article.

hi @Mark, I am sorry but you're completely wrong!  I've added some more info

"literally every photo, ever, taken digitally of a prop." is an unnecessary and certainly wrong hyperbole.

@Bergi Hmm; I believe a spinning prop must in fact exhibit those two effects on an image taken with a digital "shutter".  (Sure, it could be "really small" in some domains.)  I do apologize for getting worked-up though :)

You can get multiple propeller images close together from a rolling shutter, but you cannot get multiple propeller images overlapping.  Further, the image in the question shows clear evidence of a long exposure time, while increasing the multiplication effect requires a short exposure time.

@Mark that's why the question on the details of the camera. Surely for film an exposure is just that. Using electronic shutter it gets a bit more involved..

hi @Mark - your comment that you can not get them "close enough that they are overlapping" is really not sensible in any way.  You can get any gap between the fake-propellors by, varying the domain of the geometry and timing involved.  Also, it's a truly unreal idea that the optics involved would "know" how wide the propeller is (from a given angle?) and "not" make the images that close!

hi @Mark ... "while increasing the multiplication effect requires a short exposure time"  I have never, ever heard that and I work with digital cameras for a living.  If you have somehwere you read that, I would love to know, thanks.

@Fattie, mechanical shutters have a top speed of around 1/200 of a second.  To get higher shutter speeds, the camera starts closing the rear curtain of the shutter before the front curtain finishes opening.  In order to get a large number of propeller blades, the gap between the curtains needs to be quite narrow so a fast-moving propeller shows up as distinct blades rather than a continuous blur.

@Mark - you must be as old as me, which is incredible :-)  digital cameras (generally) don't have shutters (either the leaf one you mention or any other mechanical shutter)

@Fattie, Modern pocket cameras and cell phone cameras don't have mechanical shutters, but digital SLR cameras and other "pro" cameras generally do have. My own personal camera gives me the option either to use the focal plane shutter or, to operate in a purely electronic mode.

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text:
On video equipment used to help assemble the X-59
On 2020 Dec 14, NASA reported on Lockheed Martin's construction of the X-59.

NASA’s supersonic X-59 assembly team marks wing milestone.

The report's photos include an unexplained apparatus, comprising what looks like two Panasonic video projectors and two video cameras mounted on a stand. Green markings on a wing being assembled, and on one of the worker's arms, may be coming from these projectors. The stand might be mobile, because it's missing in this overview.

Any authoritative details are welcome, such as:

Does this apparatus have a name?

If it guides workers, how do they use it?

What are its capabilities and limitations?

What are the cameras for?

Why does it need more than one projector and camera?

So many questions

The system may have many names depending on detailed configuration, but it is  basically a mixed reality assisted manufacturing system.
One example is described in this pdf document.
The system consists of at least one projector that projects a predesigned guidline on a workpiece, to assist human workforce in their tasks. Additional hardware may include

camera(s) to document work and/or follow the progress and enable switching to new guidline projections as work proceeds; recognize different workpieces
sensors to verify correct orientation of workpiece
manipulators to reposition the workpiece as the work progresses
text or audio output further guiding workers as the work progresses (possibly the aforementioned camera verifies each step).

Depending on resolution of the projectors, the accuracy of the system might reach accuracy of millimeter scale, for example for the purpose of drilling holes into a workpiece, but it is best suited for work such as in the picture:

highlighting necessary tasks
providing guiding for correct order of tasks
highlighting "no go" areas or such on a workpiece
etc...

The bigger the workpiece, and/or the more complex the shape of it is, the less accurate the guidline picture projection will be. This can be overcome to some extent by using multiple projectors, but the system quickly becomes very complicated especially with workpiece with complicated contours.
This could be called a poor man's AR goggle, with the benefit of being rather low tech, but the downside of the workers limiting the visibility of the guidline pic as they move around the workpiece.
There most probably are two projectors on this system simply to cover a lager workpiece. Another solution might be to verify correct 3d orientation/placement of the workpiece by overlapping two guidline images, but the orientation of the projectors in this picture are such, that the images cast by the projectors do not seem to fully ovelap.
I was unable to quickly locate it, but there is a fine video of this type of system being used on assebly line of the F-35 fighter. I will keep looking...

So Lockheed Martin is a "poor man" :-)

well not exactly, being totally honest the AR headset technology is still not quite where it should be, google glass (or whatever it is called now) and hololense are getting there, but this projector thingy is kinda foolproof. Too many variables and possible bugs in headsets still...

A poor example of laser instruction projection.

Bounty is much appreciated

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text:
Strange C560 flight over the Netherlands - circling and extreme variations in altitude. Possible reconaissance or military?
Last night around 24.00 I noticed a plane flying very low over my house. Intrigued, I tracked the flight on FlightRadar and went digging for records. It turned out to be Cessna 560 Citation Encore+, registered to Aerowest (a German charter operator) with C-DAWR as registration. It took off from Hannover international airport a few minutes after 11. Over the course of the next few hours, the plane exhibited some very strange behavior:

It circled over Barendrecht 5 times
It looped over Amsterdam Schiphol airport, passing directly over one of the main runways at an altitude of ~700ft at its lowest
From 00.25-00.37, it climbed 34.825ft

It then proceeded back to Hannover, landing exactly two hours after it took off.
I read on Wikipedia that some of the Cessna 560 models are used by the US military, but they don't appear to have any based in Europe, and there isn't an air base in Hannover. Aerowest appears to be civilian operator. What could be an explanation for this flight?
Image source

This is likely a textbook example of nothing more than a training flight.

My first thought was night training with approaches and holds too.

...and a missed approach thrown in for good measure.

It only looks strange to a non aviator
This is a pretty typical training/practice/burn some fuel flight. What actually happened;

they were inbound to the airport and likely issued a hold south of Roterdam  to decent
They exited the hold and were vectored onto the approach for runway 06 at Schiphol airport.
Executed a nice stepped decent on approach
Either did a touch and go or executed a missed approach (hard to say but they came down pretty low)
Winds were likely calm and it looks like they came back for a landing/low approach on runway 27.
Touch and go/go around/missed and back home to where ever they started.

This is pretty standard, maybe the pilot needed to keep his IFR currency or just wanted to get some practice holds and approaches in

Thanks! I guess I was mostly confused because it happened at night

@Benthlin in some jurisdictions night currency is separate from day currency so you need to do a certain amount of flying at night as well as in the day. It may also be the case that it was simply when the pilots had free time to deal with the practice flight.


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How does ATC control / separate Airbus Industrie test flights?
Airbus is testing a A321 (D-AVXA, flight AIB97XA) around Toulouse this morning. The test is at low altitude, with many speed and altitude changes, including touch and go (maybe rolling slowly on the runway):

Source: FlightRadar24.
This path crosses other commercial routes / VFR aircraft, and it seems unlikely altitude, speed or even position can be anticipated all the time, but could be determined only while in flight.
All these constraints surely mean a specific treatment from ATC. How does ATC control and coordinate this flight with other aircraft? Toulouse Blagnac (LFBO) is open to commercial flights, and this test flight was within or close to Toulouse TMA.

Like all other flights .. they send a flightplan and get a clearance :) Maybe you should try to specify your question

Sure they can .. ATC is there to provide a service to the pilots, not to limit their options.

At least in the USA, they wouldn't even need to file a plan.  They could depart VFR, and operate freely, as long as they obey appropriate speed restrictions (250 kts below 10,000 feet, less in certain airspaces) and stay in VMC conditions.

@Federico, Please don't. I had the same feeling before checking, and both forms are used, even on Airbus site. Anyway it seems it comes from GIE Airbus Industrie, an entity that doesn't exist anymore. (a GIE is an alliance in French law.)

They will be in contact with ATC at all times and ATC can issue a clearance to operate within a defined area or within a specific flight level range, keeping other aircraft out of that area, e.g.

APP: AIB97XA, cleared for turns and flight level changes in 20NM radius around ABCDE intersection, between FL70 and FL145 at your discretion.

or a bit more standard phraseology:

APP: AIB97XA, cleared for turns and flight level changes in 20NM radius around ABCDE intersection and maintain block FL70 until FL145.

From what is visible in the French AIP, the TMA airspace of Toulouse has airspace classes D and C from different altitudes up to FL145, also in the area where your mentioned flight happened.

(Source: German NfL 1-251-14 Verfahren Sprechfunk / P. 47)

@mins Cant provide citation for that, but all other flights will be either above FL145 since it is enroute traffic and the adjacent upper CTA controller does not clear aircraft into that airspace to descent, or it will already be below FL70 and under the same ATC unit that the Airbus Test Flight is, so the controller will not assign these level anyway. But yes, any such close or block usage will be coordinated to adjacent sectors.

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text:
Why is the turn coordinator gyro tilted?
I’ve read many places (such as the FAA’s Instrument Flying Handbook) that a turn coordinator can sense both roll rate and turn rate due to the gyro being tilted 30 degrees.
However, why does tilting it do this, vs a turn and bank indicator without the tilt? I’m looking for an explanation of the applied physics and how the mechanisms inside the instrument turn that into a useful indication.
I do understand the principles of rigidity and precession, or at least how they apply to the attitude indicator and directional gyro, so no need to rehash those unless my question indicates I don’t actually understand them as well as I think.

Realized I just answered a new question that might be considered a duplicate of this.  My answer there also is relevant here -- see https://aviation.stackexchange.com/questions/100128/in-the-turn-coordinator-the-gyro-is-canted-30-degrees-from-the-horizontal-so-i/100135#100135  Btw note that the spin axis of the gyro wheel is not canted in the turn coordinator, rather the gimbal axis is.

The turn coordinator is a rate gyro. Unlike attitude and heading gyros that are free to rotate and the instrument senses the orientation of their axis, the turn coordinator (and the turn indicator one) has the axis mounted fixed and the instrument measures the torque forces as the gyroscope tries to resist the rotational motion.
With the axis mounted along the longitudinal axis in a turn rate indicator, banking the aircraft does not apply any torque to the axis, so it is not reflected by the indication. Only turning does.
But with the axis mounted tilted 30° in the turn coordinator banking also causes change in the orientation of the axis, so it is also detected.
The benefits of a rate gyro are that it cannot tumble in unusual attitude, because there are no gimbals, and that it does not accumulate any drift. Those are especially useful in a spin where the attitude indicator will likely have large error, but the turn coordinator still indicates correctly so you can reliably tell which way you are spinning to correct it.

I was unaware of the lack of gimbals in the TC; that plus the axis explains exactly what I was missing!

@StephenS note that in modern “glass cockpit” avionic suites all the gyros are rate ones (either vibrating or laser ring), one for each axis, and the attitude is integrated in software. That is mechanically simpler, so more reliable, and if the math is done correctly, cannot tumble.

They kind of work in two stages; you get an initial bank indication from the roll axis movement, plus the yaw action coming in as heading starts to change, but roll stops as you get to the bank angle and hold it and from that point the indication is from the yaw motion.  You get a more instantaneous indication, and yaw motions without bank are inhibited, helped further by an internal hydraulic motion damper.   Regular TBs have no damping.  If you fly with a regular T&B in an airplane that wags its tail in bumps, it can be pretty challenging on partial panel, the needle going like a metronome.

@JanHudec, pedantically, we like to call those gyrometers in my field (autonomous flight). It is a bit of any oxymoron to call them rate gyroscopes as the definition of a gyroscope is "a device used for measuring orientation", which the solid-state device clearly does not do.

@StephenS and Jan H- Actually these instruments do have one set of gimbals. There are centering springs that tend to keep the gyros in a fixed position relative to the aircraft but there is some motion. For more detail see comments https://aviation.stackexchange.com/questions/100128/in-the-turn-coordinator-the-gyro-is-canted-30-degrees-from-the-horizontal-so-i#comment279504_100135 and https://aviation.stackexchange.com/questions/100128/in-the-turn-coordinator-the-gyro-is-canted-30-degrees-from-the-horizontal-so-i#comment279506_100135 and answer http://aviation.stackexchange.com/a/81919/34686.

(Ctd) So the springs do form part of a "torque meter" but not in a way that eliminates all motion and allows the orientation of the gyro wheel to remain perfectly fixed relative to the aircraft.  There is movement about the gimbal axis.  As we know, the gimbal axis is purely fore-and-aft in case of turn rate indicator, and canted upwards in case of turn "coordinator".


text:
Why choose a seaplane for crew rotation at sea, supply of spares to ships, long-range search and rescue and surveillance?
The Indian government has been discussing with Japan since on buying Shinmaywa US-2 aircraft which would be used for various roles such as crew rotation at sea, supply of spares to ships, long-range search and rescue and surveillance according to Flight Global.
The partnership is strategic for Japan that seeks to contain the rise of China and India that can not get an alliance with Pakistan, but that, we do not care. It is also the return of Japan to the club of countries selling international aircraft.

Yet, my question is : why choosing such an atypical airplane for such missions ? In France I know that SAR missions are done by Falcon 50 and 200, which are long-range business jets, or helicopters. Neither of them are able to land at sea but jets are faster and helicopters have divers to be to take care of the SAR mission.
For crew rotations, it is true that the US-2 can carry up to 20 people. And if this kind of missions only concerns large boats where my lack of knowledge in the Indian Navy suggests to me that they still have helipads, the NH-90 carries as many troops as the US-2 and can even land directly on it if it has one. Furthermore it can land anywhere, but the sea indeed.
Thus why choose a seaplane for search and rescue, crew rotation at sea, supply of spares to ships, long-range search and rescue and surveillance ?
To my mind, their is lots of positive aspects using this aircraft as far as it would enable them to be faster in crew rotation at sea, supply of spares to ships but to be slower for SAR and surveillance, which seems to me to be the most important mission. Is it a difference of philosophy between French and Indians ? Or is their a deeper reason to prefer seaplane ?

Speed and range, compared with an helicopter, obviously.

a Falcon is good for search over a large area, not so good for actual rescue.  A heli is good for search and rescue in a relatively small area, not so good for for large area or long-range. A sea plane is a good balance between the two.

The US-2 is an amphibious airplane not a pure seaplane, it can land on water and land. MTOW is a bit higher on land as well.
Purely logistics alone means that a single craft type is better.
It is better to have a jack of all trades than a bunch of specialists when building out your fleet unless you have immediate need for those specialists.
Each aircraft type that gets added to the fleet has its own maintenance handbook, maintenance schedule, set of spares, their own type rating, etc.
Helicopters have smaller tanks and can't stay in the air as long or get out as far away from base. They also cannot carry as much stuff as the US-2 can. They would be handy for search and rescue and supplying helipad-equipped vessels. However not all ships will have a helipad.
Jets cannot land out at see so they can only do the search part of search and rescue. They cannot do any supplying out at sea that doesn't involve putting the packages on a parachute.

Quite interesting point of view. Do you have references that proved that was th reason Japanese or Indian government used to chose this amphibious airplane ?

@Marine1: The answer give logical reasons, but we all know that governments aren't logical.  How could we know why the Indian government actually did anything, unless they stated their reasons?  (Even then, we'd have to wonder whether they were being truthful: could be just that the Japanese manufacturers bribed the right people :-))

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Do Cargo fly very short routes?
Let's say that a package has to travel from point A to point B. These places are not located in the same Country, nor are such Countries adjacent to each other. Example: point A is in Italy, point B is in the United Kingdom.
The package is not delivered directly. From tracking info made available by the Company, you find out the package leaves point A and reaches Rome. Then it reaches Bologna, and later Dusseldorf, Germany. It then reaches Barking, in the United Kingdom. From here, it reaches Tamworth and then gets delivered to point B. These legs are pretty short, if you map them, so my question is:
could the package have traveled by air in any of such legs? or do Cargo companies prefer other means in this situation?
EDIT
I am not referring to the use of wide body aircraft on short-haul. Rather, I want to figure out if contracting out the delivery of goods over short-haul routes is a common practice among Cargo airlines. If this is true, how could a given package remain within the network of the Company?

Can you be more specific about what you mean by contracting out the delivery?

Yes. It means "hiring" a subsidiary to perform the delivery.

You might want to watch the Top Gear episode where Hammond and May race the Royal Mail (season 13, episode 4). You will note that the Royal Mail extensively uses aircraft between locations on the British Isles, which I guess is a pretty short haul. This would answer your question as yes, they do.

OK, since names are emerging, let's give things their name. The example I mentioned is the true delivery network of UPS. So, @sanchises, do you think your answer applies to them as well?

@FrancescoCastellani I wouldn't know why not - all the places you mention have an airport. Of course, they might operate their own planes on these routes, so it's impossible to know for sure without inside information - perhaps you can check the track&trace timings and see if they're even possible by road?

It might make sense but in this case it sounds weird to me that there is a plane leaving London City Airport (the closest to Barking) at 9pm and landing at Birmingham Airport at 12am. Three hours? Naaaah... If I could I would definitely opt for inside information :)

@FrancescoCastellani That's almost certainly a truck. They will normally use trucks for short distances, not airplanes. Much cheaper.

It's important to note that delivery companies like UPS and FedEx usually have their sorting facilities at or very near airports to facilitate air cargo. Even boxes that are shipped by truck will go through the airport sorting facility.

It's fairly common for cargo, freight, and mail to be carried by aircraft - particularly for high value or priority cargo.
For example Royal Mail (the primary British mail service) uses short haul flights for distances of less than 100 miles (London Stansted to East Midlands Airport), along with around another 10 flights within the UK, every night.
These flights are used for priority (next day) mail, but will be filled with "cheaper" mail if necessary.
It all depends on the value of the cargo and the speed which it needs to travel, and aircraft only tend to be used where it is profitable to do so (ie where the cargo needs to travel fairly quickly and they can charge a high price to justify that).
Generally trucks will be used for shorter distances (<500 miles) for low value cargo, and for longer distances for heavier cargo or cargo which does not need to travel quickly.
http://www.eastmidlandsairport.com/emacargo.nsf/content/customer_royalmail
https://en.wikipedia.org/wiki/Royal_Mail#Fleet

In your example it depends on the service. Since UPS is mostly a ground service company it will almost always move by ground transportation. The only time they would move it by air is if the shipment is air service and has a sooner delivery commitment. Moving freight by aircraft is always going to be more expensive than putting it on a truck or a train. If they can make their delivery commitment without flying it they will.
If the shipment is moved through air service then it is more likely to move by aircraft. In this case it depends not only on distance but location within the system. If the origin and destination are both within the same "market", I.e. serviced from the same airport, then there will be no reason for it to go on a plane. Outside the market    anything that has an overnight delivery commitment will go on an aircraft to a hub where it will be sorted and flown to the airport that services the destination. In situations where there are numerous large markets in very close proximity, such as the US east coast, they may be able to accomplish this by ground transport.
With regular mail often government postal systems will have a certain amount of space allotted for them on commercial aircraft, both freight and passenger.

Within a Cargo company, who takes all the decisions you mention in paragraph #2? Btw, your standpoint is very interesting - the closest to inside information that I can get! Thanks!

I can't tell you much about how those decisions are made but that would be the job of the logistics department and aircraft dispatch. And I don't envy their jobs! They have to figure out how to move things efficiently and react quickly to all situations, especially weather.

Sometimes with UPS even their cheaper delivery options will come by air if the distance is very long. For example, I live in Tennessee, so shipments from California frequently come by air via their air hub in Louisville. Stuff from the East coast will usually just come by truck, though unless you get priority. As a side note, it's interesting to watch flightradar or flightaware in the early morning hours, when Memphis and Louisville become the busiest airports in the Americas and among the busiest airports in the world. - haha


text:
How do airlines provide crews for the return leg of a long-haul flight?
In a video, a Swiss International Air Lines crew flies an Airbus A340-313 (flight LX38) from Zurich to San Francisco. Then, they can be seen (I am not sure if this is on the very same day) visiting downtown and the Golden Gate prior to getting back to the airport for the return flight (LX39), which is scheduled for departure around three hours later.
The question here is:
How do airlines handle crew turnovers in long-haul flights?
Is it the same crew who is demanded to command the return flight? Or is there, oddly enough, a replacement crew in each destination airport? Or do they carry the crew for flight LX39 onboard flight LX38?

Where does the video say the same crew explored the city and then piloted the turn flight three hours later? Regulations side, It would be completely impossible to go for a leisurely bike tour to Marin and get back to the airport with enough time to preflight the trip. Based on the video, they could have spent the next week in SF. We don't know.

And an extra dose of shame for the folks riding their bikes on the sidewalk on Market St.

How can they even think to stroll around like tourists with such a short layover is out of my mind - simple.  They didn't.  I nearly always find it best to assume that professionals act professionally.

Related, how do the airlines replace a crewmember who falls off their bike at a distant outlying field and cannot fly home?

Short answer: The airlines rent the hotel(and often breakfast services) and let crew live in. Extra bonus is also given to them in daily base.

Why the down votes? Was the question too stupid to ask? I am sorry if I am not a Nobel Laureate.

You're right.  I can't see a reason for the down votes and a down vote without a comment is just a "drive by" annoyance.  +1 to do my bit to restore CAVOK.

@FC84 because of the assumption of professionals beying "stupid enough to stroll around instead of working". you removed that, I will remove the -1.

@Simon you should NOT upvote to revert someone else's downvote

@Federico I am sorry, I didn't mean to offend anybody. It was clearly not in my intentions. Glad you pointed this out, thanks.

@federico - equally you should not downvote for a statement you dislike, at least not without a comment. Improve the answer, or comment why you downvoted. Otherwise what's the point in downvoting for anything other than clear poor quality overall?

@Federico I have exactly the same right to upvote as you do to downvote.  And I always leave a comment.  I could equally say you should not downvote without commenting.

You presume that they flew back the very same day... but that is an incorrect presumption.
For long flights over about 8 hours, strict rest limits apply so they cannot fly again for 8-10 hours at a bare minimum. Typically, a crew from a long-haul flight will stay in a hotel in the destination city for anywhere from 12 to 48 hours, depending on the flight length, timezone changes, airline schedules, union contracts, and so on. Yes the hotels and travel bonuses costs the airline a pretty penny but that's the cost of doing business.
So at this very moment there will be 1 or maybe 2 LX crews, resting (or touristing...) in San Francisco, waiting to fly a return service.
For more information you can google or ask a new question on Fatigue Risk Management Systems.

USA, EU, as well as other countries, have set law to regulate daily duty hour. Both the actual flight time for pilots and time of gap between shift have been limited. In USA,the rule has been tightened after Colgan Air Flight 3407 incident .
Most of the airlines rent hotel nearby the airport of long-haul destination for the cabin crew and pilot. Usually the airlines will schedule the crew to service the return flight for next day. The crew often receive extra bonus (in terms of local currency) from the airlines.
Special immigration policy are set for air crew, many countries are allowed to air crew entry with via crew certificate and on duty, regardless the general immigration and visa policy. On the other hand, some countries have introduced Crew Visa System such as USA(C-1/D visa).
Sometimes the air crews, especially the pilot, are requested to travel to other destinations as passengers by another flight. It depends on the airlines' schedules. In such case the off-duty crews may also travel by freighters, like El Al Flight 1862 incident.

For long routes, quite often the crew of the outbound leg is not the same as the crew on the inbound leg.
For example the way KLM does it (or used to) to Curacao where there were 3 flights a week, they'd have the crew fly Amsterdam-Curacao, then have a few days off on the island before taking the next aircraft back, the crew of which would then have a few days off.

Depending on the destination city the route may be more or less desired by crews obviously, some places are much nicer to spend a few days on company time than others :)

Flights to the Maldives are the same for airlines that do a weekly flight - the airline puts the crew up in a resort for a week! As you can imagine everyone tries to get that route, it's seen as a perk.


text:
What are the recent developments in the satellite-based tracking of aircraft?
I find it pretty unsettling that in 2016 it is still not possible to track transoceanic flights using flightradar24 or flightaware, because of lack of coverage.
When the unfortunate MH370 accident occurred, I stumbled upon news of the British company Inmarsat launching, or discussing the launch of, a series of satellites to help track transoceanic flights anywhere in the World, that could also be useful to determine vertical separation.
Quite a few months have passed and I seem to have lost track of this. So I am here to ask those who know more about it:
what are the recent developments in the satellite-based tracking of aircraft?

https://aireon.com/ is another company you may find interesting

The German Space Agency (DLR) worked with ESA to track flights from space using ADS-B, the same technology behind flightaware etc.
Some info about it is here
A commercial entity, called Aireon, is planning a global constellation to monitor aircraft that will piggy-back upon the next generation of Iridium satellites. But, unfortunately, the recent setbacks to SpaceX launch capabilities have delayed Aireon's schedule. The first launch of the Iridium-NEXT satellites occurred on Jan 14th 2017 and the entire constellation - providing near global ADS-B coverage - is planned to be complete by mid-2018.
Aside from ADS-B, there is also research going on to track aircraft through their exhaust emissions (something I'm working on right now). Nothing is published about that yet, though.

Can we have an update to this answer now that there are some Iridium-NEXT birds in orbit?

@UnrecognizedFallingObject updated!

Everything has been developed already. Geostationary satellites cover +/- 70° latitude. Many aircraft are equipped to communicate through geostationary satellites for telephony, internet, or tele-monitoring. In the MH370 event, the engines (!) have sent some data packages to the manufacturer. This is how we got to see these circles of MH370's last position, even though the position was never transmitted over satellite.
It would be very simple to transmit the GPS position through satellite. Only  while flying over the poles, communication would be slightly more complicated.
Of course, somebody would have to pay for the data bandwidth. To do it, or not is merely a commercial decision, and not a technical challenge any more. One fact that is easily overlooked is that constant monitoring would add very little to aircraft safety. How much are the airlines (and the travellers) willing to spend to make the relatives of crash victims feel better?

Geostationary satellites are sufficiently far away that the 70° latitude restriction is solely due to near-surface effects. A plane 30.000 feet above either pole can communicate with all geostationary satellites.

@MSalters This is unlikely. Antenna elevation for GEO satellite is 0° around 80° latitude, about -8° over the pole. A top mounted antenna has no line of sight when cruising over a pole. Side mounted antennas would be possible, but the signal attenuation due to the long path through atmosphere goes significantly up, and the noise due to ground interferers goes up as well. An excessive power margin would be needed to maintain a useful SNR. Do you have any example for civil aircraft maintaining a link to a GEO sat over a pole?

Whoops, my bad. That should be 80 kilometers above the poles, which is 250.000 feet, so 30.000 feet is way too low. Another problem would be that you may have line of sight, but many satellites use fairly narrow beams so they don't waste power. It can be a design decision to not cover areas north of 70° latitude.

Just because FR24 and Flightaware don't show anything doesn't mean that the information is not available.
FR24 and Flightaware are not the only systems out there; there are several others if you care to search, and many of them are not subject to the same restrictions as FR24 and FA.
There are already (and have been for quite a few years) uplinks and downlinks from the various ATC agencies and aircraft. If you know  which satcom frequency bands, and have a suitable decoder program, it is relatively easy to 'eavesdrop' upon the uplinks and downlinks. Many aircraft are already sending their positions on a regular basis, and it's just a case of plotting them all.
For example, at the moment I'm seeing almost 30 aircraft crossing the north Atlantic, and each of these is 'out of range' of the regular ADS-B listeners who feed data into FR24 and Flightaware.

Here's an image of the north Atlantic during a busier period (07.30am UTC)

This isn't really a solution, however, as it's not comprehensive. For example, you can 'see' 30 aircraft but there are far more than 30 aircraft over the atlantic at any given time. The fraction that get missed is important: And that's far higher with a ground-based system such as this rather than using satellite-based ADS solutions.

There are initiatives taking place to provide satellite based ads-b service to aircraft. As a caveat, this doesn't necessarily mean that you will be able to see the data on FR24 or FA via the internet, at least the way it is currently. The implementation is through a complicated network of various entities.

ICAO  Since the disappearances of AF447 and MH370 hey have created the Global Aeronautical Distress Safety System (GADSS)  which will allow airlines to be able to track aircraft anywhere on earth. This is just a set of standards the airlines must comply with. It's intended to go into effect in 2018.
Aireon This is a company formed as a joint venture between Nav Canada, which is the Canadian ATC provider, and Iridium, a communications company that operates a network of satellites. Iridium is launching the next generation of satellites into orbit and through Aireon they will be providing ads-b service.
FlightAware As well as the information you can see on their website they now offer fee-based access to their large database of flight information and tracking data.
Globalbeacon This company was formed as a partnership between Aireon and FlightAware. (Like I said, complicated) This company will provide global tracking service to airlines through FlightAware's web infrastructure so they can be compliant with GADSS. [Btw, they have an implementation timeline on their site. ]
SITAOnAir This company provides airborne Wi-Fi, cell phone and passenger entertainment services. They also provide flight planning services to the airlines. They are partnering with Aireon and FlightAware to add ads-b tracking to the services they provide the airlines. [This company was originally formed as a joint venture with Airbus.]

Since this is a conglomeration of governmental, private, non-profit and United Nations organizations, each plays a part in the implementation of of worldwide satellite coverage.
What is somewhat unclear is how this will effect the publicly accessible tracking info. Flightaware will certainly have the capability to add trans-oceanic data, but they seem to be adjusting their business model toward providing data to paying corporate customers. I don't find any information as to whether or not global coverage will become a part of the website.
FlightRadar24 operates mostly on a network of volunteer hosts with ads-b receivers. They won't have access to satellite data unless they enter into an agreement with one of the above companies. Once again, I can find no information as to whether this is in the works or not.


text:
How does ATC deal with a crew who is not capable of a clear pronunciation?
It probably is common guesswork to think that in nowadays' World we all speak English no matter what our mother tongue is. This should be even more the case with Civil Aviation, where everything is in English and the staff is hired also based on its linguistic capabilities, yet the question arises:

How does the ATC deal with a crew who is not capable of a clear pronunciation? The opposite might also happen.

What to do in such cases?

It doesn't affect the question but is worth noting that English is not the only official ICAO language. You can be serviced in English anywhere but if you are in Canada you'll hear plenty of french and over Mexico you'll hear almost entirely Spanish comms.

"we all speak English". You should travel in Africa or some other countries in Europe of Middle East to learn that this is not even close to true.

Well, let's say it is a given-ish then!

(-1) The question is full of bias and unnecessary assumptions and could be easily improved by removing all the fluff.

The unnecessary assumptions were made to give an example. You are being all but relaxed.

@Relaxed While I agree that the first sentence isn't true in a lot of places, it is actually mostly true in the context of international civil aviation for almost all of the world. It's an ICAO requirement for ATC and pilots flying to or through airspace where they don't speak the native language.

@reirab Yes but that's not what's stated and the sentence is in any case unnecessary so there is no need to debate this, the question would unquestionably be better without it regardless. Similarly, I find the fact that all the examples go in the same direction (third-world pilots with US ATC, whereas the issue also exists with European pilots or strongly accented native speakers being difficult to understand for everybody else) somewhat irritating.

@FrancescoCastellani I used to be called Annoyed, so there you have it. But you could easily edit the question and I would happily relax and upvote it.

Consider it done!

@reirab Rereading it, the first sentence is even explicitly not about aviation since it goes one with “This should be even more the case with Civil Aviation”.

@Relaxed Right, that's why I said it isn't true in a lot of places. We're agreed that the first sentence isn't correct.

So how do you propose to change it?

@FrancescoCastellani Personally, I'd just remove the first sentence and change the second one to something like "While English proficiency is generally required by ICAO for international civil aviation, communication difficulties still sometimes arise with non-native speakers, regional accents, or even poor radio signal reception."

In the same way that native-born Americans, purporting to speak English, sometimes cannot be understood by other native-born Americans who speak English.

From a legal standpoint English is not only the official language of aviation but you must be "English Proficient" to legally fly at least here in the US. This is both an FAA and ICAO requirement these days. Although what happens when a repeat is needed has been covered in other answers it should be noted that accents should not stand in the way of communications and you may, depending on your case be required to have an "English Proficient" endorsement on your license. In reality there should never be a pronunciation issue (but we live in a far from perfect world)  Here is the full ICAO chart of grading,

(source)
Here is some interesting info on the dangers of language differences in aviation accidents.
As for the fact that some aircraft radios garble signals and don't help in transmitting marginally acceptable audio all while in a plane with near defining engine noise; that is a whole separate question...

You don't need to be English proficient to legally fly. You need to be proficient in one of the languages applicable to your CAA's jurisdiction OR English. You can fly legally with only LP German lvl 4 in Germany and no English proficiency, because German is one of languages used in R/T (VFR only).

Added to reflect this as a US/FAA requirement

There is special phraseology snippets that allow information to be transmitted over the frequency with more accuracy, slower, repeated or worded differently.
ATC may also query other company traffic to relay information in another language or they might use the ACARS/CPDLC system to transmit a text message, should both parties be capable.

SAY AGAIN
„Repeat all, or the following part, of your last transmission“

(Source: AIP Germany GEN 3.4)

WORDS TWICE
„Request: Communication is difficult. Please send every word, or group of words, twice.
Information: Since communication is difficult, every word, or group of words, in this message
will be sent twice.“

(Source: AIP Germany GEN 3.4)

SPEAK SLOWER
„Reduce your rate of speech“

(Source: AIP Germany GEN 3.4)

To add to this: Any intersections, fixes etc. which are hard to pronounce for non-native speakers can be easily said out in phonetic alphabets. For e.g. "KLMAN" would simply become Kilo Lima Mike Alpha November for those who don't use it regularly.

Why English teachers don't always make the best pilots: "You mean more slowly, young man!"


text:
What is the runway holding short line on Taxiway B between B2 and B3 at KFAT for RWY29L?
At Fresno Yosemite International Airport (KFAT), I was instructed to taxi to RWY 29L via B11, B from Signature Support. When passing B3 and approaching RWY 29L end, I noticed there is one holding short line between B2 and B3 and the next one is on B2, I was confused where to hold short for the instruction (hold at the first anyways).
The one between B2 and B3 seems extra, but it is a double-solid-double-dashed line, which is also shown the Google Map the same I observed. I am wondering how this can well-define a runway protection area? Meanwhile, the first holding short line (the one between B2 and B3) does not mark which runway it protects. I also suspect it should have been ILS protection marking instead.

Google Map Link to KFAT Airport

FAA Airport Diagram for KFAT

That’s a hold line for aircraft taxiing on Bravo while large aircraft are departing Rwy 29L to prevent aircraft from taxiing behind the blast pad for 29L and potentially being tossed around by the jet blast from the departing aircraft.

I am not sure I follow. Do you mean the hold line on taxiway B (b/w B2 and B3) or the one on B2?

Hold traffic cleared to taxi to 29R short of Bravo 2 for a departing aircraft on 29L.

It makes sense that Line 1 is a hold line for Taxiway B2. I am still surprised to see a hold short line is marked when both sides are movement areas.

If atc wants you to hold at the first line, how would they say it? Would they say “hold short of B2” or what?


text:
Is there a roadmap to satellite / inertial only based navigation?
GNSS is the most accurate mean of navigation available on the flight deck but it relies on satellite being available and under control. Inertial systems are autonomous, but far less accurate.

While GNSS and inertial systems relieve authorities from the burden and cost of building and maintaining terrestrial navaids, terrestrial navaids (VOR/DME) are still imposed as a safety net in case instruments fail (GNSS) or drift (inertial).
As a matter of fact it's not possible to deliver an IFR certificate to an aircraft without a VOR-DME navigation equipment.

Note: Taking comments into account, this last sentence may be not true for IFR certification in the US. However flying IFR in controlled airspace, or flying some approaches may mandate VOR/DME/ADF, depending on the country. E.g. "ADF, DME: Until about 2013, the UK Air Navigation Order required an ADF for all IFR in controlled airspace. The ADF requirement now remains only for instrument approaches that contain an NDB." (source).

Is there any credible roadmap to remove those constraints and have IFR aircraft relying only on GNSS/Inertial? If so what are the mainlines of this new framework?

There is an effort to reduce VOR's to a "minimum operational network", however there are no plans to remove VOR's completely at this time. Until they fully commit to removing VOR/DME stations (or at least letting them rot as a number are), I'm not sure that there will be an available timeline. This may run after NextGen is fully implemented but as far as I can read there is no provision in NextGen to completely remove ground based navigation sources.

Are you sure you can't get an IFR certification without VOR/DME? FAR 91.205(d) and (e) states equipment requirements and doesn't specify VOR/DME, only "Two-way radio communication and navigation equipment suitable for the route to be flown", which means you can use just RNAV if the airports you fly into have RNAV approaches.

@RonBeyer: Well, maybe it's not required in the US to certify the aircraft. How do fly "DME required" or "ADF required" approaches, like this one? Missed approach fix is still often defined relative to a VOR or sometimes an NDB no?

@mins Sometimes, but for RNAV approaches the missed approach fix is usually a named fix you can select in your GPS. Could you imagine having to reconfigure for VOR/DME navigation during an RNAV missed approach? Sounds like a recipe for accidents... For example RNAV KGRB 24 lists the missed approach procedure as "Climb to 2500 direct to KILBY and hold" which is just a named fix.

@RonBeyer: Maybe in that case, the RNAV approach wouldn't be allowed without DME. I was reading this for Europe, but it's too complex for me... it is likely regulations are being adjusted to take GNSS substitution capabilities into account, but this task has not been completed yet.

@mins That document says that in many cases, GPS can be substituted for DME. It specifically cites the SR20/22 which is sold in Europe without DME or ADF, just an IFR approved GPS.

I read a few years ago that they were working towards "combo" avionics boxes which combined GPS and LORAN (of all technologies).  This would still be ground based, but based on an upgraded LORAN chain which requires very few ground stations and work over long distances and higher power output which make it harder to jam, and therefore a good backup for GPS.

@Lnafziger: Interesting point, thanks. That's actually mentioned in this document about the enhanced Loran project (E-Loran). E-Loran has the advantage of broadcasting an accurate time signal which could backup GPS time too.

I'm not aware of any program at present that does away with ground based infrastructure completely. Present plans are to have the ground based stations as a backup in case of a GNSS outage/interference.
The present FAA plan, for example includes DME while reducing the VOR coverage:

Navigation- En Route Transition; from FAA navigation Programs Update Sep 2013
As far as ground based navigational aids are concerned, the plan is to reduce the VOR coverage with VOR Minimum Operational Network (MON) as a middle step. However, the plan appears to be to retain DME at the expense of other Ground Based Navigation Systems (GBNS).
FAA's Alternative Positioning, Navigation, and Timing (APNT) project is geared up towards maintaining aviation operations in case of a GNSS outage. According to FAA:

The Alternative Positioning, Navigation, and Timing (APNT) project is investigating alternatives for providing higher precision back-up for Global Positioning System (GPS)-based position, navigation, and timing (PNT) services.

However, Ground Based Systems are still a part of the program (though VOR is not) and serve as a backup for the GNSS. One of the options is to modify the existing DME facilities in order to improve coverage/accuracy.
International Civil Aviation Organization (ICAO) 2013-2028 Global Air Navigation Plan also stresses the importance of having some 'conventional' ground based systems as a back-up for GNSS:

Conventional navigation aids (VOR, DME, NDB, ILS) are in widespread use globally, and most aircraft are equipped with the relevant avionics. The vulnerability of GNSS signals to interference has led to the conclusion that here is a need to retain some conventional aids or alternative navigation service solution as a back-up to GNSS.

ICAO also concurs that DME is the most appropriate ground based equipment to be used in the future navigation system:

The implementation of PBN will make area navigation operations the norm. DME is the most appropriate conventional aid to support area navigation operations(i.e. assuming DME multilateration on board capability),since it is currently used in multi-sensor avionics for this purpose.

At present, as far as I'm aware, there is no available roadmap for satellite/inertial only based navigation systems as far as civil air transport is concerned. Though GNSS will remain the primary means of navigation for the foreseeable future, plans still retain ground based systems as a backup.

Are any of the RNAV systems out there able to read VOR/DME signals or would you need an older receiver in case of GNSS failure?

FMS is a multi-sensor system that is capable of reverting to IRS, DME/DME, or VOR/DME  navigation if GNSS is unavailable.


text:
What is the role of the flight dispatcher? How do the dispatcher and the flight crew interact?
The flight dispatcher is known as the ground pilot.

Air Canada flight dispatcher (source: On the job: Flight Dispatch)
It's not clear to me what is their role related to a given flight, or where are they working from, how the interactions occur between the flight dispatcher and the flight crew, or the maintenance team.

Have you ever been waiting for your flight at an airport and noticed that big roll of paper being printed up at the counter? That is called the "Flight Release". That roll of paper has all the information that the pilots need to fly their flight. It has their fuel, their route, the weather information, probable payload, and everything else they need. A Flight Dispatcher put that together for them.
The pilot looks it over and calls the Dispatcher if there are any questions. The aircraft cannot push back until both the Captain and the Dispatcher agree that it is safe to do so.
Once the flight is airborne the Flight dispatcher keeps an eye on that flight and makes any recommendations to the Captain regarding any change in route, altitude, speed, destination or anything else relating to flight safety and the efficient operation of the flight. This is called "flight following". If ATC gives the Captain a route change, the Dispatcher will calculate the new fuel burn. If the flight has to hold, the dispatcher will calculate how long the flight can hold before it has to land somewhere.
The Captain and Dispatcher communicate with each other while the aircraft is in flight primarily by ACARS. Think of it as an instant messaging system between the Flight Deck and the Dispatcher's computer. They type messages back and forth to each other and each sees the message on a screen.
The Flight Dispatcher is also there to help if there is a problem with the flight, i.e., a sick passenger, a mechanical issue, a change in the weather, or any other problem that the Captain may be facing.
The Captain and Dispatcher have joint authority to initiate, delay, continue, deviate, or cancel a flight. Nothing can happen until they both agree on a plan of action. Because of this the FAA considers the dispatcher to be a "crew member" and the Dispatcher's base of knowledge is very close to that of the pilots. Because of this, Dispatchers are allowed to ride up in the Flight Deck if they want to and are required to do it at least five hours a year.
No, the Dispather is not an Air Traffic Controller. However, the Dispatcher's plan for the route is given to ATC. ATC then takes all the flight plans filed by all the Flight Dispatchers who work for the airlines and put them all together for the big picture and then make it happen.
In short, the Flight Dispatcher works for an airline to plan flights and give that information to both the flight crew and air traffic control, monitor the flights while they are airborne, and work with the Captain to solve any problems that may arise. Their main concerns are, in order, flight safety and flight efficiency.

Welcome to aviation.se -- very nice answer!

Thank you for this nice explanation Gary. Are you working as a dispatcher?

Yes, I work as an airline Flight Dispatcher.

Bear in mind the "Flight Dispatcher" role is more a North American one. In other countries, there is no 'Flight Dispatcher'. Pilots get a flight plan from the Flight Planners, and see their fuel uplift/baggage/freight data from Load Control, and manage the rest themselves. They contact load control or flight planning directly if they have issues, and contact central ops during the flight if they have issues. It's not a universal role.

Essentially, dispatcher:

Prepares flight plans and briefings. This includes adjusting the route
according to the weather to e.g. take advantage of the winds,
reserving slots with network manager (in the areas that have one) and
collecting all data pilots will need like weight and fuel estimates.
Handles disruptions. When a flight can't depart as scheduled or needs to divert,
whether for technical or external reasons, the dispatcher finds
replacement crew and equipment or rebooks the passengers, might
reschedule other flights to make any necessary replacements available
and so on.
In case of diversion, if there is a choice, advises pilots on
where to divert to minimise the disruption to the overall operation.
E.g. flight from hub might return even if it could complete the leg,
because the problem would be hard to fix in the original destination
while flight towards hub might continue even if it will have to
divert midway, because that way a replacement can be sent to meet it
at the diversion point etc.

So in a sense they are the bridge between the technical and business side: instructing the technical people on what to do to keep the operation cost-effective.
On the image, the left screen is a map, most likely showing where each aircraft is, the middle looks like scheduling tool with timeline for each aircraft and pilot and the right is probably some flight planning software.

Update: @mins found this video about the flight planning process. And it is a lot of work. When flying multiple short legs, there is no way pilots could do it themselves when with smaller aircraft they may only have around 40 minutes turn-around time.

authors: Богдан Давид


text:
How do terms apron, ramp, tarmac, taxiway, parking area, gate, hardstand relate to each other?
The terms apron, ramp, tarmac, taxiway, parking area, gate, hardstand are used in a way that I cannot understand.

Boeing Everett Factory. Photo by Andrew Hunt at Airliners.net (url unknown). Cropped image from this page
I can't figure out if one is generic and another a part of this set, or if they are well defined by their use (taxiway), or anything else.
Questions I can't answer:

Is this a binary split: Runways vs tarmac?
Is the gate stand part of the tarmac?
Is a parking area different from a ramp?
Is a taxiway considered part of the apron?
Are aprons made of Tarmac (tarmacadam)?
Is a de-icing area part of the ramp?

etc.
In addition I guess this may varies between countries and/or aeronautical jurisdiction.
Can someone provide an accurate view of the lingo and explain whether some are related or synonymous? (filling the blanks if some important term is missing).

Apron and ramp (in US) mean the same, though the official term is apron. FAA Advisory Circular Number 120-57A Surface Movement and Guidance Control System defines it as:

Apron (Ramp). A defined area on an airport intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance.

Now, the apron includes parking, maintenance and service areas, including taxi lanes.

The apron area includes the following components:
(1) Aircraft Parking Positions.  Intended for parking aircraft to enplane/deplane passengers, load or unload cargo.
(2)  Aircraft Service Areas.  in or adjacent to an aircraft parking position.Intended for use by personnel/equipment for servicing aircraft and staging of equipment to facilitate loading and unloading of aircraft.
(3)  Taxilanes.  Apron areas which provide taxiing aircraft access to and from parking positions.
(4)  Vehicle Roadways Markings.  Identified rights of way on the apron area designated for service and Aircraft Rescue and Fire Fighting (ARFF) vehicles.

So,

Is this a binary split: Runways vs tarmac?

Kinda. Basically, the areas in airport where aircraft are involved are divided (by the FAA atleast) into runway, taxiway and apron.

i.  Movement Area.  Refers to the runways, taxiways, and other areas of an airport which are used for taxiing or hover taxiing, air taxiing, takeoff, and landing of aircraft,exclusive of loading ramps and aircraft parking areas.
j.  Non-movement Area.  Refers to taxiways and apron areas that are not under ATC
Is the gate stand part of the tarmac?

Its part of ramp, so yea.

Is a parking area different from a ramp?

It is part of the ramp/apron

Is a taxiway considered part of the apron?

Nope. As already noted.
FAA AC No: AC 150/5300- 13A Airport Design defines runways and taxiways as:

Runway (RW).  A defined rectangular surface on an airport prepared or suitable for the landing or takeoff of aircraft.
Taxiway (TW).  A defined path established for the taxiing of aircraft from one part of an airport to another.
Are aprons made of Tarmac?

Tarmac is a trademark of Tarmac limited, which supplies construction materials for a a number of airports (among others), though most of the aprons are actually made of concrete.

Is a de-icing area part of the ramp?

As de-icing is part of servicing, it should be part of apron/ramp.
However, it should be noted that though this is the 'official' version, differing local usage means that tarmac is used interchangeably with apron/ramp.

Adding the possible origin of "apron": From theater apron stage, which makes more sense than the clothing piece often assumed. (Apron could come ultimately from Fr. napperon (mat), due to the circular shape.)

Quite a bit of these can be found in the Pilot-Controller Glossary:

APRON− A defined area on an airport or heliport
  intended to accommodate aircraft for purposes of
  loading or unloading passengers or cargo, refueling,
  parking, or maintenance. With regard to seaplanes, a
  ramp is used for access to the apron from the water.

Ramp and Apron are synonymns:

RAMP−
  (See APRON.)

TARMAC is not, by itself, defined, however there are a number of terms related to operations on tarmac, for example:

TARMAC DELAY− The holding of an aircraft on the
  ground either before departure or after landing with
  no opportunity for its passengers to deplane

Leading me to believe that any place can be considered "Tarmac" except movement areas.
Taxiway is also not explicitly defined (oddly, I'm sure it is well defined in the airport construction guide), but high-speed taxiway is. I assume a taxiway is the same thing except a more reasonable speed:

HIGH SPEED TAXIWAY− A long radius taxiway
  designed and provided with lighting or marking to
  define the path of aircraft, traveling at high speed (up
  to 60 knots), from the runway center to a point on the
  center of a taxiway. Also referred to as long radius
  exit or turn-off taxiway. The high speed taxiway is
  designed to expedite aircraft turning off the runway
  after landing, thus reducing runway occupancy time.

Although I don't believe all taxiways are required to be lit. So I would say Taxiway is:

Taxiway: A defined path for an aircraft leading from runways to parking areas, hangers, gates, cargo terminals, or other operations area's.

Parking Area and Gate are not defined in the PCG, these terms should be pretty easy so I'll give a go at it:

Parking Area: Specified location(s) on the airfield where aircraft may be parked for extended periods of time.
  Gate: Designated passenger loading/disembarking area for access to terminals, other gates, and airport entrance/exits.

Hardstand is also not defined by the PCG, but Wikipedia gives it a good go:

Hardstand: A hardstand is a paved area for parking heavy vehicles.

So to answer your questions directly:

Is this a binary split: Runways vs tarmac?

Yes, since you can have a "Tarmac Hold" but not typically hold on the runway, I would say that airports do not consider the runway a part of the tarmac.

Is the gate stand part of the tarmac?

Yes

Is a parking area different from a ramp?

A parking area can be different from a ramp, but is not always. For example at an FBO, the parking area and the ramp are usually the same. The parking area for airliners is probably not on the ramp though.

Is a taxiway considered part of the apron?

No, since the apron is defined and intended to accommodate aircraft for the purpose of loading/unloading, etc. These are not operations you would perform on a taxiway.

Are aprons made of Tarmac?

They can be in the sense that they can also be made of concrete, asphalt, etc.

Is a de-icing area part of the ramp?

Yes

Tarmac is indeed a material... https://en.wikipedia.org/wiki/Tarmac

@Porcupine911 Thank you, fixed.


text:
In what portion a non-GPS approach, can a pilot legally fly with GPS as primary navigational resource?
In IFR-GPS-equipped (/G) aircraft, a pilot flies most of the segments with GPS as primary navigational resource* even the route is along victor airways or VOR radials. However, when we start the approach, we have to switch the nav source from GPS to the nav source specified for the approach. In this context of using GPS for non-GPS approaches,

When should a pilot switch away from GPS? Is it from an IAF, FAF or upon ATC vectors to intercept the final approach course?
If the a pilot executes a missed approach, when can the pilot switch back to GPS? Is it when established on course direct to the holding fix?

*By primary navigational resource, I mean it provides the signal/data source for the CDI needle on a HSI, that a pilot, autopilot or flight director refers to make actions or action suggestions.

An appropriately installed GPS may be used until crossing the final approach fix on a non-localizer approach, and until the segment requiring navigation via the localizer on a LOC, ILS, SDF, or LDA approach. It's generally approved and legal at any other time.
During the missed approach, a pilot may switch to GPS immediately, unless the missed approach requires navigating by using the localizer, in which case the ground-based navaid must continue to be used until the procedure no longer requires navigation by reference to the localizer.
The FAA covers this in AC 90-108:

An otherwise
  suitable RNAV system cannot be used for the following:
a.   NOTAMed   Procedures.
  Unless otherwise specified, navigation on procedures that are
  identified as not authorized (“NA”) without
  exception by a NOTAM. For example, an operator
  may not use a RNAV system to navigate on a procedure affected by an expired or unsatisfactory
  flight inspection, or a procedure that is based upon a
  recently decommissioned NAVAID.
b.   Substitution on a Final Approach Segment.
  Substitution for the NAVAID (for
  example, a VOR or NDB) providing lateral
  guidance for the final approach segment.
c. Lateral Navigation on LOC-Based Courses.
   Lateral navigation on LOC-based courses
  (including LOC back-course guidance)
  without reference to raw LOC data.

As a non-expert in aviation, I had no idea about this. It's more than a little concerning. Are aviators generally aware how insanely susceptible GPS is to not only jamming but also spoofing?

@BarryTheHatchet It's Die Hard 2 all over again. :)

@BarryTheHatchet I'd love to discuss in more detail - care to talk about GPS approaches in chat?

What if the NAVAID signal is monitorred, but the FD uses the GPS for input? (GPS overlay)

Substitute and alternate have specific meanings in this context and for non-LOC approaches I don't know if this answer is correct.  For LOC approaches the ability to monitor raw data could also influence what is allowed, although I believe the FAA urges/requires primary navigation using the localizer but I can't find this in writing.

WAAS is also a factor. Best for any pilot to read AC90-108, now with change1, in full. However it is still a bit ambiguous because it says in one section that final segments must always use the primary type of nav aid, but later under 11[b] it says WAAS TSO-C145/-C146 equipment may be used as an alternate without restrictions and as a substitute if satellite availability is calculated prior to the procedure(in planning)

authors: Vladimir F Героям слава


text:
Does an amended shortcut clearance change the clearance limit?
A typical IFR cleared route is like,
KABC VOR1 V12 VOR2 V23 VOR3 V34 VOR4 KXYZ
Suppose the verbal ATC clearance is "N7890, you are cleared to KXYZ airport, KABC.ZYBUD departure, radar vector VOR1, V12 VOR2 V23 VOR3 V34 VOR4 then direct, climb and maintain 3000, expected 5000 5 min after departure, departure frequency is 123.45, squawk 4321"
While you are en-route on V12, ATC says "cleared direct to VOR3". Does this new clearance change the clearance limit from KXYZ to VOR3? If no further clearance is issued while approaching VOR3, should we hold at VOR3 or continued with the cleared route firstly obtained?
POST EDIT:
The context is within US.

I assume that this question is about the US, based on your examples.
No, it doesn't change the clearance limit. For some reason I could only find the documentation in the ATC orders, not the AIM. Section 4-2-5 of the orders says:

Issue a clearance “direct” to a point on the previously issued route.

PHRASEOLOGY−
  CLEARED DIRECT (fix,waypoint).
  Or
  CLEARED DIRECT (destination) AIRPORT.
NOTE− Clearances authorizing “direct” to a
  point on a previously issued route do not require the phrase “rest of
  route unchanged.” However, it must be understood where the previously
  cleared route is resumed. When necessary, “rest of route unchanged”
  may be used to clarify routing.

If the clearance limit changes, the controller will usually give you a completely new clearance to copy.

It doesn't change your clearance limit. If it were to change your clearance limit, he would have issued you a new clearance Instead of "cleared direct ..."
Usually it goes something like this:
"N123, I have an amended clearance for you. Advise ready to copy"
"Approach ready to copy"
"N123, you are cleared present position to ... "
 And then CRAFT.


text:
What are the guidelines to execute a missed approach during circling?
Alice is approaching KTCY on RNAV (GPS) RWY 12 at KTCY circle NE to RWY 30. When she is turning right base to RWY 30 final, she loses visual contact with runway environment and decides to go missed. Spotted her GPS map, she notices she is right over the RWY 30 touchdown zone. How should she execute the missed approach?

a) Climb to 700 (600 to 700, HDG 300˚), Climb left turn (~left 260˚ over circling NA region), 3000 direct ECA hold.
b) Climb to 700 (600 to 700, HDG 300˚), Climb right turn (~right 100˚) 3000 direct ECA hold.
c) Climb right turn (~right 100˚) 3000 direct ECA. Note Alice is above circling minimums 600 and initial climb to 700 is based on a HDG of 120˚.
d) Continue fly over LNAV MAP, make a right 180˚, then climb 700, climb left turn 3000 direct ECA hold

In more general senses, does circling nullify the initial climb, initial turn portion for a missed approach procedure, so that we may choose to intercept the following course, navigational radial, or direct to the fix from the side we turn with less degrees?

Flying a missed approach while circling can require some judgement, as the procedures are designed to originate at the missed approach point. Going missed while circling can mean starting the procedure some distance away from the MAP. The goal of the initial procedure should be to intercept the published missed approach course, while maintaining obstacle and traffic clearance. Put another way, a pilot may deviate from the letter of the procedure, if doing so follows the spirit of it.
In this situation, I would recommend option B. The procedure will provide obstacle clearance when started from three points: 443 MSL and about 4000 feet from the RW12 threshold (LPV minima); 638 MSL and about 11,500 feet from RW12 (LNAV/VNAV); and 600 MSL over the RW12 threshold (LNAV and circling). The procedure assumes you can climb at least 200 ft/nm, so to climb 100 feet would require less than 3035 feet across the ground. This puts you within the area where the published missed approach starts. Once you reach 700 feet, you can turn directly to the VOR and continue the procedure as published. The initial turn would normally be towards the landing runway, but in this example the runway is straight ahead.
If you descended below circling minima and needed a significant climb to get back, consider circling over the airport until either reaching 700 feet before flying towards the VOR.
The FAA has recommends the thought process above in the AIM, section 5-4-21. Emphasis mine:

5-4-21 (c): If visual reference is lost while circling−to−land
  from an instrument approach, the missed approach
  specified for that particular procedure must be
  followed (unless an alternate missed approach
  procedure is specified by ATC). To become
  established on the prescribed missed approach
  course, the pilot should make an initial climbing turn
  toward the landing runway and continue the turn until
  established on the missed approach course. Inasmuch
  as the circling maneuver may be accomplished in
  more than one direction, different patterns will be
  required to become established on the prescribed
  missed approach course, depending on the aircraft
  position at the time visual reference is lost.
  Adherence to the procedure will help assure that an
  aircraft will remain laterally within the circling and
  missed approach obstruction clearance areas. Refer
  to paragraph h concerning vertical obstruction
  clearance when starting a missed approach at other
  than the MAP.

[...]

5-4-21 (h): ... In the event a balked (rejected) landing occurs at a position
  other than the published missed approach
  point, the pilot should contact ATC as soon as possible
  to obtain an amended clearance. If unable to
  contact ATC for any reason, the pilot should attempt
  to re−intercept a published segment of the missed approach
  and comply with route and altitude
  instructions. If unable to contact ATC, and in the pilot’s
  judgment it is no longer appropriate to fly the
  published missed approach procedure, then consider
  either maintaining visual conditions if practicable
  and reattempt a landing, or a circle−climb over the
  airport...

The AIM includes a diagram that demonstrates a pilot turning against the missed-approach instructions when that is the safer course. The missed approach requires a climbing right turn to the VOR; the pilot in the scenario on the right chooses to make a left turn as that allows the initial climb to take place over the airport.

Source: FAA AIM

This is what ICAO specifies

If visual reference is lost while circling to land from an instrument approach, the missed approach specified for that particular procedure shall be followed. The transition from the visual (circling) manoeuvre to the missed approach should be initiated by a climbing turn, within the circling area, towards the landing runway, to return to the circling altitude or higher, immediately followed by interception and execution of the missed approach procedure. The indicated airspeed during these manoeuvres shall not exceed the maximum indicated airspeed associated with visual manoeuvring. (ICAO Doc 8168: PANS-OPS, Volume 1, Chapter 7, Section 7.4)
  Related Articles

This is a good reference. however, it does not specify whether we may take a shortcut to intercept the second leg.

This is a written exam question. According to sporty's practice test, the correct answer is: make a climbing turn toward the landing runway and continue the turn until established on the missed approach course.
AIM 5-4-21 states the pilot should make an initial climbing turn toward the landing runway and continue the turn until established on the missed approach course.

Can you please cite your sources for this answer?


text:
When an alternate minimum applies, does it change MDA or DA?
In US, the weather minimums for an alternate airport are typically 600-2 for precision approaches and 800-2 for non-precision approaches at ETA, unless otherwise specified at US Terminal Procedure Publication.
When it comes when we actually fly the approach,

a) Is the DA raised to 600 for precision approaches?
b) Is the MDA raised to 800 for non-precision approaches?
c) Is the visibility requirement raised to 2SM for approaches at an airport?

Do alternate minimums work similar to inoperative components, use of alternate altimeter settings, NOTAM to change the actual minimums we use to fly, or a purely preflight planning number for selecting alternate airport?

I don't think they affect the actual approach at all. They affect whether you can put that airport in your flight plan as alternate. But when you are there, you shoot the approach as defined. Or you shoot it anyway, because you don't have fuel to go anywhere else any more.

From the FAA Instrument Procedures Handbook, section 6-4: "The 600-2 and 800-2 rules, or any exceptions, only apply to flight planning purposes, while published landing minimums apply to the actual approach at the alternate."

this has the makings of a good answer, but I think it needs more explanation.

I guess you could add " Alternate limits are just artificial flight planning limits.  If you can't land at the intended destination you will have an increased margin of weather limits because the weather should be well above normal minimums when you reach the alternate airport."

@rbp - I think this answer is fine: correct, succinct, and to the point.  Published landing minimums apply... what else needs be said?

i won't rewrite what's already on meta: http://meta.stackexchange.com/a/7659/157449


text:
What are the implications of Visual Descent Angle Not Authorized (VDA NA)?
On some non-precision approach plates, there is a VDA/TCH mark. My understanding of it is information-only. If you pass its starting fix at the charted altitude and maintain the given descent angle, the airplane will flying over the runway thresh hold at TCH.
However, I noticed one NOTAM mentions this information is not authorized, e.g. E16 RNAV (GPS) RWY 32 (on Nov 2019).

!FDC 9/9659 E16 IAP SAN MARTIN, San Martin, CA. RNAV (GPS) RWY 32, ORIG-C... GELVY TO RW32: 3.37/45 NA. 1903201729-2103201728EST - (From FAA website on 2019/11/22)

Given "GELVY TO RW32: 3.37/45" is still one spatial path for the non-precision approach, and the LNAV approach is still available. There are no airport elevation and re-defined fix height. So my questions align with,
1) Why am I not authorized to fly "GELVY TO RW32: 3.37/45", if my airplane is capable to maintain descent angle and have runway environment in sight right above MDA.
2) Are there any additional procedures to follow even for flying VDA/TCH at an airport when are authorized?
E16 RNAV (GPS) RWY 32

--

This NOTAM is a Flight Data Center (FDC) NOTAM which is used to amend published Instrument Approach Procedures (IAP).  That means this NOTAM is effectively amending the procedure as the FAA hasn't had the opportunity to change the procedure yet.  This is probably due to a new obstruction that has been placed in the decent path.  Perhaps a new cell phone tower has been erected.  That is why it is always a good idea to check NOTAMs especially when flying under IFR.
EDIT:  To clarify a comment I made to OP, the MDA usually requires 350 feet obstacle clearance along the final approach segment.  However, when flying a glide path, the Required Obstacle Clearance (ROC) increases the farther away you are from the threshold (see graphic from Code 7700 Website).
The ROC is based off of the Obstacle Clearance Surface calculated for the approach.  Notice that if a new obstacle is erected somewhere along the glide path it is possible for the MDA to still be satisfied but the glide path ROC may have to change.  That is probably why the MDA is not changed in this NOTAM but the glide slope is Not Authorized.
Quote from 7700 website:

(1) If the OCS is penetrated, the OCS slope may be adjusted upward, thereby increasing the glide path angle. The glide path angle would increase because it is dependent on the required slope.

However, the obstructions (if any) do not affect the MDA per NOTAMs, the VDA/TCH path is still protected until MDA. So I suspect there are additional obstruction clearance for VDA/TCH if specified?

On the final approach segment of an approach without vertical guidance like this one, 350 feet of obstacle clearance is needed on the final approach segment.  It is possible that at that descent angle a new obstruction would have gotten too close to the glide path.  See this site for more info:  http://code7700.com/doa_required_obstacle_clearance.htm

This reminds me an article discussing a case when LNAV MDA is lower than LNAV/VNAV DA due to different obstacle clearance measurement: https://www.boldmethod.com/learn-to-fly/navigation/when-lnav-minimums-are-lower-than-vnav-which-should-you-use/